Chronological enamel hypoplasias have long been considered to reflect general health and nutritional status during amelogenesis. However, the relationship between undernutrition and enamel defects in humans is still poorly understood. The objective of this study is to determine the effects of nutritional supplementation of the prevalence and ages at development of enamel hypoplasias and other developmental defects of enamel (DDE) in chronically undernourished children. This project includes a field study in Tezonteopan, Mexico. Here, is 1968, Chavez and Martinez (1982) began a longitudinal nutritional supplementation study of undernourished children. Forty-two pairs of infants were randomly assigned at birth to either a nutritionally supplemented or non-supplemented (control) group. These individuals have been continuously supplemented and monitored (for morbidity, growth, and development) up the present time. They have now reached ages (11 to 19 years) at which most permanent teeth have erupted and their enamel quality can be examined. In this study all erupted teeth will be evaluated following the FDI (1982) classification for the presence of DDEs. Anterior teeth will be photographed to further document the appearance and location of defects. The location of defects will be used to provide an estimate of the ages at development of the defects. Statistical analyses will focus on difference between supplemented and control groups in both the prevalence and age at development of defects. The proposed study provides a unique frequently found worldwide, affects the occurrence of enamel defects. These data will provide a better understanding of the etiology of enamel hypoplasias and, by extension, the nutritional requirements for normal enamel development. As these defects are relatively permanent and time specific they have great potential as rapid assessment indicators of nutritional status early in life.